Biomimetic Anti-Icing surfaces for eco efficient ice-slurry generators – COOLISSE

To reach these scientific objectives, the COOLISSE project is divided into two main parts, one dedicated to the manufacture of surfaces and the other to their characterizations. In this project, both experimental and numerical approaches will be used for rationally designing surfaces with anti-icing properties. Dealing with the fabrication part, main investigated parameters will be: (i) the surface micro and nano-structuring, (ii) the properties of the surface chemistry and (iii) those of the impregnating oil to hold it in place, a crucial parameter for surface durability.
Based on FRISE and DVRC expertise, and dealing with the characterization, set-up and methods will be developed to study in detail: (i) droplet formation/nucleation of ice crystals according to surface characteristics, (ii) monitoring of droplet crystallization (formation kinetics linked to topography), (iii) heat transfer dynamics, measurement of the adhesion of the ice on the surface and finally (iv) the design of a device to study the influence of the flow in cooled environment. It is also proposed to study the influence on the generation of crystals on the heat transfer as well as the introduction of periodic local modification of surface, such as a succession of alternate wetting and non-wetting zones, capable of generating local recirculation. Then, a global numerical method will be developed to describe the thermal equilibrium state, heat flux and gas-liquid-solid interface changes in both static and dynamic conditions. Our main objective is thus to systematically study the mechanism of action of the surface on anti-icing, during freezing and phase change.

COOLISSE project could lead to scientific breakthrough on scientific fields where interactions between liquid and surfaces at low temperature are concerned (food applications other than slurry generation, aviation, aerospace, ...) but also between two surfaces (such as solid/solid friction). For example, the developed surface technology can have many applications for surfaces in frosting conditions, such as in heat exchangers or icing on planes. Non-icing surface heat exchangers (HX) are of major importance, as the ice layer is a barrier to heat transfer, reducing the global efficiency of the HX. Moreover, electrical energy (joule effect) is necessary to regularly defrost the HX or the cooled surface (planes). Limiting frosting thus will have a high impact on the global energy consumption for refrigeration.

COOLISSE project is directly linked to strong environmental issues: efficient ice slurry generator will increase the development of secondary refrigeration. This technique has a significant impact on the environment by reducing the refrigerant by a factor of 10, which is in line with the F-gas regulation. The use of phase change materials (PCM ice) is very efficient when combined with thermal storage. It is therefore suitable for renewable energies (solar and wind) because of its ability to store energy when it is available and to release it at peak times. The overall power of the installation can then be reduced, and when the storage operates at night, the efficiency of the system is higher due to the lower air temperature. This technology is therefore suitable for dealing with recurrent heat waves. In addition, these innovations must be carried out in such a way as to reduce the impact of these new materials on the environment throughout their life cycle (design/manufacture/use), in accordance with the principles of the circular economy.
The direct economic consequences are a gain in terms of maintenance and energy costs related to mechanical movement (scrapper free). Indirectly this will also promote the implementation of this secondary refrigeration technology which, being very efficient, will then become competitive. It can be envisaged that this technology and its operating conditions could be outsourced to a refrigeration player. After a short training, the refrigeration technicians will be operational.
From a social impact point of view, the communication around our project and its results will lead to an increased awareness of the environmental impact of refrigeration among the public we will target. From an academic point of view, if all partners agree, and after all patentable results have been protected, results will be published. Publication of research results is essential as: rapid publication in top journals ensures the use and the application of the results within the scientific community, industry (through ‘Poles de compétititivité’ Euramaterials et CIMES) and to the public.

Not concerned at present

Secondary refrigeration is an effective way to drastically reduce the quantity of primary refrigerant fluid used while improving energy efficiency by storing and transporting energy-dense secondary fluids. These ice slurries, made of ice crystals suspended in aqueous solution, are unfortunately not yet widespread due to an over-investment related to scraped surface or supercooling type generators. Within this COOLISSE project, our objective is thus to participate in the energy optimisation of the refrigeration sector by designing new type of ice slurry generators. Our aim is therefore to develop stainless steel surfaces where formed ice could be carried away by the fluid flow, without rotating scraper blades.
These original non-wetting micro/nanostructured surfaces, inspired from nature, displaying anti-icing properties will be obtained by an original and efficient combination of processes: additive manufacturing (to yield micro-structures) and femtosecond laser ablation (to reach nanometer scale roughness) that will allow obtaining a multiscale and very dense textured stainless steel surface. These surfaces will be then infused by inert liquid in order to obtain slippery infused surfaces (SLIPS). The second objective of the project is to develop methods and expertise on the surface characterization under flow at low temperature [-15°C to 0°C]. The potential in anti-icing applications of the designed surfaces will be proven by investigating their action mechanisms on ice formation, analysing the freezing time, adhesion strength and nucleation in the freezing process. In parallel a comprehensive numerical method will be developed to describe the thermal equilibrium state, heat flux and gas-solid-liquid interface changes during freezing and phase change.
The environmental impact and potential gain of these new surfaces on slurry fabrication process will also be compared to traditional processes using multiple criteria analyses like Life Cycle Assessment.